{"record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"49ebbf3316c3dd256cb3e31290529982f82ea2adc241e2455dd96b545b3b40fb","created":"2026-10-15T23:43:22Z","files":[],"origin":{"assisted_by":["ai:gpt-5.5"],"kind":"seed"},"parents":["ce59fb6cd812fc05906d0c60a71c75ea22bc686bcf38e7c3ef7010834d98ee7b","d8a9ec10e0c8ce1f600a32f6b5e30123082ea38c1e0e558311ba655e08b94674"],"salt":"8b789fd487438314f8eed84eb285d531c827ce76b83e6f978a0b57c484437a08","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":["ai:gpt-5.5"],"external_id":"amo.muonic-atoms.muonium-spectroscopy","kind":"well-posed","literature_status":"open","n":"2","parents":[],"plain":"Muonium, an antimuon holding an electron, contains no proton, so its energy levels test the theory of light and charges without nuclear-structure uncertainty and give the muon mass and magnetism. Its best measurements date from about 25 years ago.","posed_since":"","precise":"The muonium ground-state hyperfine interval (about $4.463\\,\\mathrm{GHz}$) was last measured at LAMPF in 1999 and the $1\\mathrm{S}-2\\mathrm{S}$ two-photon interval at RAL in 2000. Improve both by at least a factor of 10 (MuSEUM at J-PARC for the hyperfine interval, Mu-MASS at PSI for $1\\mathrm{S}-2\\mathrm{S}$) and determine $m_\\mu/m_e$ and $\\mu_\\mu/\\mu_p$ from them, testing whether the two routes and QED theory agree.","problem_ref":"d8a9ec10e0c8ce1f600a32f6b5e30123082ea38c1e0e558311ba655e08b94674","references":"","settled_by":"New muonium hyperfine and $1\\mathrm{S}-2\\mathrm{S}$ measurements, each with an uncertainty at least ten times below the 1999-2000 values, combined with bound-state QED theory to yield consistent $m_{\\mu}/m_e$ values.","status_note":"MuSEUM reported ongoing hyperfine measurements at J-PARC aiming at a tenfold improvement in 2025 (arXiv 2501.02736).","title":"Muonium hyperfine and 1S-2S intervals at improved precision","topic_ref":null},"attested":{"attestation":{"batch":null,"client_id":null,"id_token_sha256":null,"kind":"platform"},"record_hash":"d77c1636e4506f6fee9b90976a80e1f42b2a1dbd9ca32725296381771f291c91","schema":"pubphys.attested/1"},"envelope":{"attested_hash":"579db7d6391a009e30eb14568e1d7817bed2d1d6c994c63290fa15799116e46c","platform_signature":{"key_id":"c6afc19b31429869751f06879c75cd64ea92654423d15b44be775bf1310a60da","sig":"6HJO9V1Z3URoSfhbA-iRgbNrmlJ3PmwnLCwHz1IiyzoG0p9HZkQCfwXoUjIohjtM7ydB7tBK7LE3eG3KZp74Dw"},"schema":"pubphys.envelope/1"},"record_hash":"d77c1636e4506f6fee9b90976a80e1f42b2a1dbd9ca32725296381771f291c91","leaf_index":2256}